The invention relates to an optoelectronic semiconductor device with a waveguide, comprising a semiconductor body with a silicon substrate on which are present in that order a first layer of a material comprising silicon oxide and having a groove and a second layer of a radiation-guiding material which forms the waveguide at the area of the groove. The invention also relates to a method of manufacturing such a device.
Such semiconductor devices are used inter alia in optoelectronic systems in the field of optical telecommunication. They are also used in systems for frequency doubling in which laser radiation with a wavelength of .lambda./2 is formed from laser radiation with a wavelength .lambda. in a non-linear optical material. The use of a waveguide is of major importance here because the radiation must remain concentrated over a larger distance for an efficient frequency doubling. The use of a silicon substrate has several technological advantages, among them the possibility of cleaving.
Such an optoelectronic semiconductor device is known from the article by S. Mann et al. "Fabrication and Characterization of Processable Polydiacetylene Waveguides" published in SPIE, vol. 971, Nonlinear Optical Properties of Organic Materials, 1988, pp. 245-251. The known device with a waveguide comprises a semiconductor body with a silicon substrate on which are present in that order a layer of material comprising silicon oxide, in this case silicon oxynitride, and having a groove, and a layer of a diacetylene polymer--a non-linear optical material--which forms the waveguide at the area of the groove. The layer comprising silicon oxide is formed by means of PECVD (=Plasma Enhanced Chemical Vapor Deposition), whereas the groove is formed by means of RIE (=Reactive Ion Etching), for which a mask having a strip-shaped opening is used. The known device is used as a non-linear waveguide or as an optical switch. The first layer must be comparatively thick for effective operation of the waveguide.
A disadvantage of the known device is that the walls and bottom of the groove are comparatively rough as a result of the etching. The roughness or raggedness of the edges of the mask used for etching also contributes to the roughness of the walls. When radiation is introduced into such a waveguide, scattering of a portion of this radiation will occur at the unevennesses in the bottom and the walls. The efficiency of the radiation transport by the waveguide is reduced by this. This is obviously undesirable. A further disadvantage of the known device is that it is not easy to manufacture: reflections occur in the comparatively thick first layer during the photolithographic generation of the etching mask. The generation of the mask is rendered more difficult by this.